Acquired immunodeficiency syndrome and related opportunistic infections are a significant cause of morbidity and mortality in susceptible population. This study aims to negate the paucity of data regarding the relation between CD4 levels, prevalence of enteric parasites, and the outcome of treatment with HAART (highly active antiretroviral therapy) and Cotrimoxazole in Kerala, India. Multiple stool samples from 200 patients in a cross-sectional study were subjected to microscopy and Cryptosporidium stool antigen ELISA. Parasites were identified in 18 samples (9%). Cystoisospora and Cryptosporidium spp. were seen in 9 cases (4.5%) and 5 cases (2.5%), respectively. Microsporidium spores and Chilomastix mesnili cysts were identified in 1 case each (0.5% each). Seven cases of Cystoisospora diarrhoea recovered after treatment with Cotrimoxazole. Diarrhoea due to Cryptosporidium spp. in all 5 cases subsided after immune reconstitution with HAART. This study concludes that a positive association was seen between low CD4 count (<200 cells/μL) and overall parasite positivity (P value < 0.01). ELISA is a more sensitive modality for the diagnosis of Cryptosporidium diarrhoea. Chilomastix mesnili, generally considered a nonpathogen, may be a cause of diarrhoeal disease in AIDS. Immune reconstitution and Cotrimoxazole prophylaxis remain to be the best therapeutic approach in AIDS-related diarrhoea.